There is a continuing need for lightweight containers so as to reduce the amount of packaging materials. This is more so the case in countries where there is a tax levied on the weight of packaging. However, besides being lightweight, the containers must be able to be shipped using a minimum of carton materials and must be easily handled by the end user. Further, after use, the container should be collapsible to decrease the disposal cost. In some countries a disposal fee is levied on the volume of material that is disposed of in the trash. The state of the art of thin walled containers, and the stacking and palleting of containers generally is set out in the following patents.
In U.S. Pat. No. 5,746,339 there is disclosed a tall plastic bottle that when empty can be collapsed by axial compression. The bottle is comprised of a series of encircling recesses which contain elongated fold starters. The fold starters in the recesses aid in the collapsing of the bottle.
U.S. Pat. No. 4,997,692 discloses thin walled bottles that are blow-molded and which have a stable base. The base has an upwardly extending portion so that there only is contact of the base circumferential edge with the supporting surface. This results in a stable platform for the base. Also, the upwardly extending portion is sufficiently strong so that in any over-pressure the center portion will not extend the upwardly extending portion to a point below the base circumferential edge.
U.S. Pat. No. 5,244,106 discloses a bottle that has built into the base a cap holder. The bottom of the bottle has an upwardly extending recess and a region to grip and hold the cap. In this way the cap can be removed and placed into the cap holder in the base to prevent the cap from becoming lost.
U.S. Pat. No. 3,485,955 discloses a pallet of stacked bottles. The bottom of one bottle rests on the cap of another bottle. The bottles are shown to be stacked in six high columns. These glass bottles are not lightweight bottles, and are not hydrostatic bottles. The contents of these bottles do not contribute to the structural integrity of the bottles.
U.S. Pat. No. 4,416,373 discloses arrays of two-piece bottles that are shrink wrapped and stacked. These can be polyethylene terephthalate (PET) bottles with a supporting base. The objective here is to set forth a way to stack two-piece bottles. It is disclosed that there should be an axial contact of the closure of one bottle with the bottom of another bottle. This axial arrangement is accomplished through the use interlocking bands on each of the bottles and shrink wrapping a series of bottles together. This assures an axial arrangement of layers of the bottles.
These patents evidence the present state of art. However, they do not disclose a very useful hydrostatic container structure or how to fill, arrange and stack hydrostatic containers. The present hydrostatic containers will have a sidewall with a plurality of encircling recesses for strength and collapsibility. In addition, the base will have a recessed well symmetrical with the vertical axis of the container. Further the containers should have a maximum of contact one to the other when stacked, and should be such that each filled container is maintained in tension. No container should be in compression. Consequently, there should be an axial stacking of the containers with a contact of the walls of the recessed base of one container with the closure and shoulder wall of a lower container. A contact or close contact of the base of one container with the shoulder of a lower container will provide for the axial stacking of the containers and for a maximum of contact of one container with another container. A contacting spacer between containers also can be used for the purpose of providing a maximum surface contact of one container stacked onto another container. All of the containers in a stack will be kept in tension due to the axial arrangement and the hydrostatic loading of the containers.